Weddigen, Erasmus. Thomas Philologus Ravennas in Saggi e Memorie di storia dell’arte, Vol. 9 (1974), pp. 7, 9-76, 149-172. Casa Editrice Leo S. Olschki s.r.l., 1974
The statue on the façade of the San Zulian church is not a saint, but an astrologer and doctor, who sold remedies for syphilis.